dwarven drills can ambush within an inch of the enemy, but howl says you can't ambush withih 18". Which rule takes precedence, or do they cancel each other out, resulting in placing ambushers over 12" from the enemy?
neither one 'beats' the other, they just determine the distance at which ambush happens. howl should trump the normal 12"ambush distance as special rules take precedence over the basic rules. but tunneler and other rules are also special rules.